When monitoring for leaks in a water supply network it is common to monitor the flow at a convenient point in the network during off-peak periods, e.g. at night, when water consumption is likely to be low or non-existent. The amount of leakage in the system can then be calculated by subtracting the anticipated usage from the measured flow.
Orifice meters are commonly used to measure flow in pipes. These work on the principle of causing water to flow through a restriction in a pipeline which results in a reduction in pressure. The flow of water can be accurately calculated from the measured pressure reduction taking into account the physical characteristics of the pipe and the restriction.
Since a flow meter must be physically connected into the pipeline it is not always possible to measure flow at any desired position in a supply network. Furthermore, the installation of flow meters at all points where flow is likely to be measured would be prohibitively expensive.
A technique commonly used for pinpointing leaks in water pipelines is to detect the noise generated by the leaking water. This can be done manually by ear using sounding sticks or ground microphones. The loudness of the sound is related to the rate of flow and the proximity of the leak. However, such a technique is only suitable for locating leaks within a relatively small area and cannot be used to provide a quantitative measurement of leakage within a large supply network.
The present invention seeks to provide a new and inventive way of providing a reasonably accurate measurement of flow at positions in a supply network where there is no flow meter installed.